Current satellite propulsion systems typically use nitrogen tetroxide with hydrazine in bipropellant class thrusters for maneuvering propulsion and use hydrazine in monopropellant class thrusters for stationkeeping propulsion. Unfortunately these satellite propellants are highly toxic and therefore, require special handling, transportation, and storage mechanisms, which add substantial cost to the deployment of satellites.
One of the goals of NASA's Discovery Program for new planetary exploration missions, is to substantially reduce total mission cost while improving performance. The performance and cost of the on-board propulsion system for satellites can be a significant factor in obtaining the highest possible science value per unit cost.
Consequently there exists a need for lower cost reduced toxicity fuels with thrust per unit mass flow and density characteristics that are sufficient to replace prior art toxic fuels. Reduced toxicity fuels have not been used in the past, due to the fact that candidate fuels are not hypergolic. In other words, liquid reduced toxicity fuels will not spontaneously react with an oxidizer to begin the combustion process as in prior art fuels such as hydrazine.
Thus, to produce a bipropellant satellite thruster for use with a reduced toxicity fuel, there further exists a need for the thruster to have an ignition element consisting of decomposing elements for decomposing a reduced toxicity propellant into hot gases. These hot gases, like hypergolic toxic liquid fuels will spontaneously react with an oxidizer and begin the combustion process.
In addition to being used with bipropellant class thrusters, there is a further need for this reduced toxicity fuel to be used with monopropellant class thrusters. As a monopropellant, the reduced toxicity fuel must have a molecular structure that will decompose into low molecular weight gases without the formation of a solid constituent such as graphite. These monopropellant thrusters must also contain decomposing elements for reforming the reduced toxicity fuel into propellant gases. Satellite fuels that can be used as both a monopropellant and a bipropellant are referred to as dual-mode fuels.